A conventional radio-controlled adjustment timepiece is described in, for example, Patent Literature 1.    Patent Literature 1: Unexamined Japanese Patent Application KOKAI Publication No. 2003-107178
Presently, in Japan, under the governing by the National Institute of Information and Communications Technology, a standard wave representing time information is broadcast. In this standard wave containing the time information, a single complete frame lasts one minute. Each time frame contains time data representing: a year (last two digits of Christian Era), total dates (accumulated number of days counted from January 1), day-of-week, hour and minute; a parity bit and spare bits, etc.
More specifically, 1 bit is represented by a rectangular pulse having a frequency, 1 Hz, and “1” and “0” are represented by pulse durations of 500 ms and 800 ms, respectively. Each of time data, a parity bit and spare bits are represented by a binary code. The spare bits indicate whether it is within or without the daylight saving time, in the case where the daylight saving time is in effect. Additionally, the carrier wave for the standard wave utilizes long waves of frequencies 40 KHz and 60 KHz.
The radio-controlled adjustment timepiece of Patent Literature 1, upon the transition to daylight saving time and the associated change of time, adjusts the kept time so as to follow the transition.
Also in the U.S., a standard wave containing such time information is being broadcast; therefore, the current time kept by a radio-controlled adjustment timepiece can be adjusted. In this circumstance, because the time information contained in the standard wave in U.S. is Coordinated Universal Time (UTC), the current time should be adjusted based on an offset corresponding to a local time zone, from the UTC. On the day of the change to daylight saving time, it is determined whether the current local time of the area is after 0 o'clock in UTC and whether it is before or after the time upon which the transition to daylight saving time takes place. If the determination revealed that it is before the time, the arrival of the time to the transition to daylight saving time is waited for, and then the display time is set ahead by one hour. If it is after the time for the transition to daylight saving time, the display time is immediately set ahead by one hour.